[Sidefx-houdini-list] Packed Disk Primitive for delayed load

Jordan Walsh jordan.h.walsh at gmail.com
Sun Feb 25 07:35:47 EST 2018


Yeah, Packed Disk prims dont really work that way. Alembic lets you have a
repository of geometry shapes (or objects) and apply transform information
to each one individually. Packed disk is just one shape with one transform.
One way around this is to save each of your packed fragments to disk
individually. Loop over the prim count and add a delete by frame number
that only keeps the same prim as the frame number. You also need to take
the packed fragments and bake the packed transforms down to points and a
transform matrix attribute. You then end up with 10 bgeo files on disk and
10 points that have a transform matrix. Then use the instance sop to
reconnect the disk files to the points with transforms, so you have 10
packed disk prims.
This works pretty well, but once you start to get to about 40k pieces (easy
to get to on big building rbd sims) you get a big delay in reading 40k very
small files off disk.

I wish there were a "packed dick fragment" type of geo that you could save
all you 40k pieces in one bgeo file (with different path attrib on each
piece), then a way to reconnect this just by giving the  "packed dick
fragment" a file path to the geometry pieces and a piece number or path.
Then just pull the transforms from the point data. This would be nice and
lean on the ifd file and the network

Jordan

On 24 February 2018 at 21:33, Fran├žois Duchesneau <houdini at trinix.ca> wrote:

> Hi,
>
> I'm trying to save packed fractured objects into packed disk primitives.
> I'm able to read the file representing let's say 10 packed objects but I
> cannot delayed load them. In other words the IFD writes all the geometry
> data.
>
> If I set the option Packed Disk Primitive on the File Sop that I render it
> does work and thanks to this I see the intrinsic:unexpandedfilename which
> tells me it can use the file reference instead of the physical geometry. My
> problem with this is that the packed primitive is now all made into one
> instead of 10. This doesn't give me access to post manipulation of the
> transform per packed primitive (one of the 10).
>
> However all this works just fine when saved to Alembic. Is it a limitation
> of Packed Primitives? If not how can I do the same without going through
> Alembic?
>
> Thanks
>
> Francois
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